High altitude electrical equipment



y 6, 1958 T. J. ANDERSON 2,833,946

HIGH ALTITUDE ELECTRICAL EQUIPMEPU Filed April 1, 1955 l/VVtA/TOI? Ol? Jimmy 191V saw I? RA/E/ Y "233334 v ALTITUDE ELECTRICAL EQUIPMENT a n: ston Company Limited, a

Trevor Lila mes Anderson, The British Thomson-Hon British company I Application April 1, 1955, Serial No 498,692 clans pant rmaments Q ain'xpm 2, 11554 4 Claims. (Cl.310 -228) This invention relatesItolelectricalequipment intended ioroperation at high altitudes or. inv other. regions of relativelyiow pressure and wateryapour; content, in'gpar- .ticular to such equipment, for example electric motors .or generators, of the kind in which electric current is trans- .ferred between relatively rotating parts of. the. equipment by means 0f ,a brush as of carbon or.graphite.on the one partmaking sliding contact witha .co-operating contact member such as a slipring or commutator on the other part. W

It is recognized that .due .to the reduction in. the amount ofiwater vapour in the atmosphere at high altitudes, brush wearis excessive. .It is also well known .thatrthe efiect .of. certain vapours, other thanwater vapour, reduces the brush wear and experiments have hitherto been conducted ,in which a suitable vapour is: introducedinto'the vicinity ofthe brush, either by. enclosing the .brushgear and the co-operating contact memberin alclosely fitting shroud and maintaining a suitable vapour. pressure, or by directing astream of vapour at the contact surface of the brush with the co-operating member.

An object of the present. invention is. tov provide for brush lubrication in a manner. whichds less elaborate and which is more economical in the. expenditurefof. vapour, so that only a relatively small reservoir. is required.

. The invention consistsin introducinga suitable vapour into. the contact area between the brush. and the co-operating contact member by feeding the vapour to the contact area through the body of .the brush.

-The vapour may bessup'plied from a small reservoir secured to or located withintthe brush 'and adapted to contain a suitable vaporisable material capable of. passing through the brush in vapour form: sthus 'theivaporisable material in thereservoir may be a suitable solid or liquid having appreciable vapour pressure :under *the expected perating condition, such thatvapour froni such'material will flow; through the brush.

Alternatively a reservoir containing's'uch material may be provided separately from the brush but in suitable communication with the body thereof. In any case means for restricting or'controllingthe fluidflo'w through the brush is interposed in thepfiuid. flow path between the- ..reservoirand the brush. Moreover a vapour chamber inay be, provided in which thevap'ou'r will collect prior touits entering the'bo'dy of thebrus i Wherethe brush is of carbon or oth 'sporous asit is contemplated'will usually be the casejthevapour may be arranged to pass to the contact area through the pores of the brush. In other cases the brush may be formed with suitable ducting for conveying the vapour through it to the contact area; such ducting may also be provided even when the brush is porous, thereby enhancing the flow of vapour to the contact area.

In carrying out the invention the vapour pressure of vaporisable material in a reservoir may be chosen such that the vapour becomes fully efiective to provide lubrication only above a predetermined altitude, or alternaiiapour' pressure of jthefrnat l iv H will be alilo'vv ofvapou'r throu'glithe restriction 7 nt "the fear Ma a .19

ice

tively the vapour pressure maybe s'u'ch that continuous lubrication is provided 'at all altitudes, increasing etfec't asthe altitude increases. I k p In orderthat the invention maybe rnore fully understood reference will now be made to the accompanying drawing, in which Fig. 1schematicallyillustrates a brush construction suitable for providing vapour lubrication in accordance with the invention, and Fig. 2' illustratesfanother arrangement employing a reservoir separate from the brush.

Referring to Figure 1 a brush of graphite say, is in use carried by a brush holder 1 and makes sliding contact with a slipring or commutator 2 of, say, copper. 'The brush 1 has secured to it, at the end remote frorri'its sliding contact surface, a reservoir 3 in the form of a small vessel the cross-sectional area of which (namely in 'a plane perpendicular to the paper) is preferably similar to that of the brush l. An open ended tube 4, secured around an opening in the wall of the reservoir 3 adjacent the brush 1, fits tightly into the body of the brush and is preferably sealed therein as by means of a sealing ring 5. A liquid or solid material 6 capable of giving ofi a suitable lubricating vapour under the expected operating conditions is contained in the reservoir 3, the material chosen being one which in the vapour state can provide a lubrinormal commutation in the cas'eof aD. C. machine. A

suitable material is, for instance, liquid trichlorethylene'as itjhas the inherent characteristic of having goodbrush lubricating properties'and is non-paste forining therewith.

Tests with such material have indicated that very small quantities of its vapour may be sufficient to reduce high altitude brush wear to almost negligible proportions, .A porous restriction 7, which may be a plug of unglazed porcelain or a metal plug having fine holes suchas'are obtainable in porous bronze, is inserted in the tube 4 to permit vapour from the reservoir 3 to flow into the bore of the tube at a rate determined, inter alia', by the de gree of porosity and other characteristics of the restriction 7. Alternatively, flowof vapour into the bore of the tube 4 could be restricted by the use of a suitable membrane, constituted for instance by'thin 'metal sh'eet, through which'the vapour can andhas to diffuse. In either case the restriction may be chosen to limit the flow of vapour to the minimum necessary for the required lubricating action. I p i In order to ensure that when the material in the reservoir 3 is a liquid it Will pass into the porous rest errand embedded at one end in the porous restriction? may: be arranged within the reservoir 3 means-a minamnesia material 6 therein, the acfiQ nofthiS WibliQ being to draw manque; into the porous restriction! Whenthe pressure outsidethebrush is 7 ina 'b'r'or theiube 4. Palm there the vapsui'pass'es nae the body of the brush 1 and makes its way through the natural pores therein, and/ or through specially provided ducts 8, to the contact surface bctwcn the brush and the slipring or commutator 2, the action being assisted by the relatively high temperature at the contact surface. To ensure that vapour appears only at the contact face of the brush it may be desirable to render the walls of the brush impervious by painting or some other suitable treatment.

In another arrangement somewhat ditferent from that just described, lubricating vapour may be supplied to the brush by means of flexible vapour conveying means, such for instance as a flexible tube leading to the brush from a reservoir mounted separately from the brush. Such an arrangement is illustrated in Fig. 2 in which a brush in a holder 11 is again assumed to make sliding contact with a slipring or commutator 12. In this case however a reservoir 13 mounted externally of the brush holder contains the liquid or solid material 14 capable of giving off a suitable lubricating non-paste forming vapour under the expected operating conditions. A tube 15 screwed into or otherwise secured to a wall of the reservoir 13 and sealed therein as by means of a plastic Washer 16 leads from the reservoir 13 and defines a vapour chamber between its closed outer end and a porous restriction 17 inserted in the tube 15 adjacent its inner end. As in the arrangement of Fig. l, Where the material in the reservoir 13 is a liquid, one or more wicks or other lengths of fibrous material 9 lying in the reservoir may be embedded at one end in the porous restriction 17. From the vapour chamber defined within the tube 15, a tube 18 communicates with the body of the brush 10 by way of a plug 19 sealed into the brush body, and to allow for movement and wear of the brush this tube 18 is made flexible by coiling it as shown within the brush holder 11 the coiled portion of the tube 18 conveniently being located within the brush loading spring 20. In passing through the top cap 21 of the brush holder 11 the tube 18 may be sealed into the top cap 21 as by a thermosetting resin 22. The operation of the arrangement of Fig. 2 should be selfevident following the description of the operation of Fig. 1.

It is contemplated that several brushes may be supplied with lubricating vapour from a single external reservoir such as 13 in Fig. 2. For this purpose additional tubes leading from the vapour chamber within the tube 15 may communicate respectively with further brushes (not shown) in a manner similar to that in which the tube 18 communicates with the brush 10, such additional tubes having been indicated at 18 in Fig. 2.

What I claim is:

1. An electrical current collector comprising a brushholder, a contact-making brush in said brushholder, said brush having a body capable of passing vapor therethrough and formed with a contact-making surface adapted to cooperate with a rotatable member electrical contact surface, a reservoir for containing vaporizable material, a vaporizable material in said reservoir having brush contact lubricating properties and being nonpaste forming in the vapor state with finely divided material of said contact-making brush, communicating means between said reservoir and a position located interiorly of said brush body and removed from said contact surface thereof for the passage of vapor from said vaporizable material in said reservoir to said brush body and to said latter contact surface, and restricting means through which said vapor can flow disposed in the path of the vapor between said reservoir and said brush body for controlling the rate of vapor flow into said brush and to said contact surface thereof.

2. An electrical current collector comprising a contact-making brush having a body capable of passing vapor therethrough and formed with an electrical contact-making surface adapted to cooperate with a rotatable member electrical contact surface, a reservoir for containing vaporizable liquid material, vaporizable liquid trichlorethylene in said reservoir having brush contact lubricating properties and being non-paste forming in the vapor state with finely divided material of said brush body, communicating means between said reservoir and a position located interiorly of said brush body and removed from said contact surface thereof for the passage of vapor from the vaporizable material in said reservoir to said latter contact surface, and flow restricting means in the form of a porous member disposed in the path of the vapor between said reservoir and said brush body for controlling the rate of vapor flow into said brush and to said contact surface thereof.

3. An electrical current collector comprising a brushholder, a contact-making brush in said brushholder, said brush having a body capable of passing vapor therethrough and formed with an electrical contact-making surface, a cooperating rotatable member with an electrical contact surface, a reservoir disposed separately from said brush for containing vaporizable material, vaporizable material in said reservoir which is non-paste forming in the vapor state with finely divided material of said contact-making brush body and has brush contact lubricating properties, communicating means extending between and connected to said reservoir and said brushholder and brush body including flexible vapor conveying means between the connection of said communicating means to said brushholder and a position located interiorly of said brush body and removed from said electrical contact surface thereof for the passage of vapor from the vaporizable material in said reservoir to said latter contact surface providing for easy movement of said brush in said brushholder, and flow restricting means through which the vapor can pass disposed in the path of the vapor between said reservoir and said brush body for controlling the rate of vapor flow into said brush and to said contact surface thereof.

4. An electrical current collector comprising a plurality of contact-making brushes, each brush having a body capable of passing vapor therethrough and formed with an electrical contact-making surface, a cooperating rotatable member with an electrical contact surface, a reservoir for containing vaporizable material, a vaporizable material in said reservoir having brush contact lubricating properties and being non-paste forming in the vapor state with finely divided material of said contact-making brushes, communicating means between said reservoir and a position located interiorly of each brush body and removed from said electrical contact surface thereof for the passage of vapor from the vaporizable material in said reservoir to said latter contact surface, a vapor chamber arranged intermediate the ends of said communicating means and communicating with each of said brushes through said communicating means, and flow restricting means through which the vapor can pass disposed in the path of the vapor between said reservoir and each brush for controlling the rate of vapor flow into said brush and to said contact surface thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,116,871 Bliss Nov. 10, 1914 1,246,825 Ster Nov. 13, 1917 1,495,657 Wagner May 27, 1924 2,703,372 Savage Mar. 1, 1955 

